Re: [PATCH v8 1/7] ata: libata-sata: Factor out NCQ Priority configuration helpers

Niklas Cassel
2024-03-08T10:03:27Z

On Thu, Mar 07, 2024 at 01:44:12PM -0800, Igor Pylypiv wrote:
> Export libata NCQ Priority configuration helpers to be reused
> for libsas managed SATA devices.
>
> Switched locking from spin_lock_irq() to spin_lock_irqsave().
> In the future someone might call these helper functions when interrupts
> are disabled. spin_unlock_irq() could lead to a premature re-enabling
> of interrupts, whereas spin_unlock_irqrestore() restores the interrupt
> state to its condition prior to the spin_lock_irqsave() call.

Seems like a mistake in the existing code, why would
ata_ncq_prio_supported_show() and ata_ncq_prio_enable_show()
use spin_lock_irq() ?

Seems like spin_lock() would be better.

For ata_ncq_prio_enable_store(), you probably want to
spin_lock_irq() or spin_lock_irqsave().

Anyway, like you said, as you are now creating helper functions:
ata_ncq_prio_supported(), ata_ncq_prio_enabled(), ata_ncq_prio_enable()
these function might no longer only be called from sysfs code,
so it is probably a bad idea to let these functions use spin_lock_irq().

However, can't ata_ncq_prio_supported() and ata_ncq_prio_enabled()
still use a simple spin_lock(), why would they need to disable irqs?

Damien, you are the author of ata_ncq_prio_supported_show(), thoughts?

Kind regards,
Niklas

>
> Acked-by: Damien Le Moal <dlemoal@kernel.org>
> Reviewed-by: Jason Yan <yanaijie@huawei.com>
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Igor Pylypiv <ipylypiv@google.com>
> ---
> drivers/ata/libata-sata.c | 160 +++++++++++++++++++++++++++++---------
> include/linux/libata.h | 6 ++
> 2 files changed, 128 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
> index 0fb1934875f2..a8d773003d74 100644
> --- a/drivers/ata/libata-sata.c
> +++ b/drivers/ata/libata-sata.c
> @@ -848,80 +848,143 @@ DEVICE_ATTR(link_power_management_policy, S_IRUGO | S_IWUSR,
> ata_scsi_lpm_show, ata_scsi_lpm_store);
> EXPORT_SYMBOL_GPL(dev_attr_link_power_management_policy);
>
> -static ssize_t ata_ncq_prio_supported_show(struct device *device,
> - struct device_attribute *attr,
> - char *buf)
> +/**
> + * ata_ncq_prio_supported - Check if device supports NCQ Priority
> + * @ap: ATA port of the target device
> + * @sdev: SCSI device
> + * @supported: Address of a boolean to store the result
> + *
> + * Helper to check if device supports NCQ Priority feature.
> + *
> + * Context: Any context. Takes and releases @ap->lock.
> + *
> + * Return:
> + * * %0 - OK. Status is stored into @supported
> + * * %-ENODEV - Failed to find the ATA device
> + */
> +int ata_ncq_prio_supported(struct ata_port *ap, struct scsi_device *sdev,
> + bool *supported)
> {
> - struct scsi_device *sdev = to_scsi_device(device);
> - struct ata_port *ap = ata_shost_to_port(sdev->host);
> struct ata_device *dev;
> - bool ncq_prio_supported;
> + unsigned long flags;
> int rc = 0;
>
> - spin_lock_irq(ap->lock);
> + spin_lock_irqsave(ap->lock, flags);
> dev = ata_scsi_find_dev(ap, sdev);
> if (!dev)
> rc = -ENODEV;
> else
> - ncq_prio_supported = dev->flags & ATA_DFLAG_NCQ_PRIO;
> - spin_unlock_irq(ap->lock);
> + *supported = dev->flags & ATA_DFLAG_NCQ_PRIO;
> + spin_unlock_irqrestore(ap->lock, flags);
> +
> + return rc;
> +}
> +EXPORT_SYMBOL_GPL(ata_ncq_prio_supported);
> +
> +static ssize_t ata_ncq_prio_supported_show(struct device *device,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct scsi_device *sdev = to_scsi_device(device);
> + struct ata_port *ap = ata_shost_to_port(sdev->host);
> + bool supported;
> + int rc;
> +
> + rc = ata_ncq_prio_supported(ap, sdev, &supported);
> + if (rc)
> + return rc;
>
> - return rc ? rc : sysfs_emit(buf, "%u\n", ncq_prio_supported);
> + return sysfs_emit(buf, "%d\n", supported);
> }
>
> DEVICE_ATTR(ncq_prio_supported, S_IRUGO, ata_ncq_prio_supported_show, NULL);
> EXPORT_SYMBOL_GPL(dev_attr_ncq_prio_supported);
>
> -static ssize_t ata_ncq_prio_enable_show(struct device *device,
> - struct device_attribute *attr,
> - char *buf)
> +/**
> + * ata_ncq_prio_enabled - Check if NCQ Priority is enabled
> + * @ap: ATA port of the target device
> + * @sdev: SCSI device
> + * @enabled: Address of a boolean to store the result
> + *
> + * Helper to check if NCQ Priority feature is enabled.
> + *
> + * Context: Any context. Takes and releases @ap->lock.
> + *
> + * Return:
> + * * %0 - OK. Status is stored into @enabled
> + * * %-ENODEV - Failed to find the ATA device
> + */
> +int ata_ncq_prio_enabled(struct ata_port *ap, struct scsi_device *sdev,
> + bool *enabled)
> {
> - struct scsi_device *sdev = to_scsi_device(device);
> - struct ata_port *ap = ata_shost_to_port(sdev->host);
> struct ata_device *dev;
> - bool ncq_prio_enable;
> + unsigned long flags;
> int rc = 0;
>
> - spin_lock_irq(ap->lock);
> + spin_lock_irqsave(ap->lock, flags);
> dev = ata_scsi_find_dev(ap, sdev);
> if (!dev)
> rc = -ENODEV;
> else
> - ncq_prio_enable = dev->flags & ATA_DFLAG_NCQ_PRIO_ENABLED;
> - spin_unlock_irq(ap->lock);
> + *enabled = dev->flags & ATA_DFLAG_NCQ_PRIO_ENABLED;
> + spin_unlock_irqrestore(ap->lock, flags);
>
> - return rc ? rc : sysfs_emit(buf, "%u\n", ncq_prio_enable);
> + return rc;
> }
> +EXPORT_SYMBOL_GPL(ata_ncq_prio_enabled);
>
> -static ssize_t ata_ncq_prio_enable_store(struct device *device,
> - struct device_attribute *attr,
> - const char *buf, size_t len)
> +static ssize_t ata_ncq_prio_enable_show(struct device *device,
> + struct device_attribute *attr,
> + char *buf)
> {
> struct scsi_device *sdev = to_scsi_device(device);
> - struct ata_port *ap;
> - struct ata_device *dev;
> - long int input;
> - int rc = 0;
> + struct ata_port *ap = ata_shost_to_port(sdev->host);
> + bool enabled;
> + int rc;
>
> - rc = kstrtol(buf, 10, &input);
> + rc = ata_ncq_prio_enabled(ap, sdev, &enabled);
> if (rc)
> return rc;
> - if ((input < 0) || (input > 1))
> - return -EINVAL;
>
> - ap = ata_shost_to_port(sdev->host);
> - dev = ata_scsi_find_dev(ap, sdev);
> - if (unlikely(!dev))
> - return -ENODEV;
> + return sysfs_emit(buf, "%d\n", enabled);
> +}
> +
> +/**
> + * ata_ncq_prio_enable - Enable/disable NCQ Priority
> + * @ap: ATA port of the target device
> + * @sdev: SCSI device
> + * @enable: true - enable NCQ Priority, false - disable NCQ Priority
> + *
> + * Helper to enable/disable NCQ Priority feature.
> + *
> + * Context: Any context. Takes and releases @ap->lock.
> + *
> + * Return:
> + * * %0 - OK. Status is stored into @enabled
> + * * %-ENODEV - Failed to find the ATA device
> + * * %-EINVAL - NCQ Priority is not supported or CDL is enabled
> + */
> +int ata_ncq_prio_enable(struct ata_port *ap, struct scsi_device *sdev,
> + bool enable)
> +{
> + struct ata_device *dev;
> + unsigned long flags;
> + int rc = 0;
> +
> + spin_lock_irqsave(ap->lock, flags);
>
> - spin_lock_irq(ap->lock);
> + dev = ata_scsi_find_dev(ap, sdev);
> + if (!dev) {
> + rc = -ENODEV;
> + goto unlock;
> + }
>
> if (!(dev->flags & ATA_DFLAG_NCQ_PRIO)) {
> rc = -EINVAL;
> goto unlock;
> }
>
> - if (input) {
> + if (enable) {
> if (dev->flags & ATA_DFLAG_CDL_ENABLED) {
> ata_dev_err(dev,
> "CDL must be disabled to enable NCQ priority\n");
> @@ -934,9 +997,30 @@ static ssize_t ata_ncq_prio_enable_store(struct device *device,
> }
>
> unlock:
> - spin_unlock_irq(ap->lock);
> + spin_unlock_irqrestore(ap->lock, flags);
> +
> + return rc;
> +}
> +EXPORT_SYMBOL_GPL(ata_ncq_prio_enable);
> +
> +static ssize_t ata_ncq_prio_enable_store(struct device *device,
> + struct device_attribute *attr,
> + const char *buf, size_t len)
> +{
> + struct scsi_device *sdev = to_scsi_device(device);
> + struct ata_port *ap = ata_shost_to_port(sdev->host);
> + bool enable;
> + int rc;
> +
> + rc = kstrtobool(buf, &enable);
> + if (rc)
> + return rc;
> +
> + rc = ata_ncq_prio_enable(ap, sdev, enable);
> + if (rc)
> + return rc;
>
> - return rc ? rc : len;
> + return len;
> }
>
> DEVICE_ATTR(ncq_prio_enable, S_IRUGO | S_IWUSR,
> diff --git a/include/linux/libata.h b/include/linux/libata.h
> index 26d68115afb8..6dd9a4f9ca7c 100644
> --- a/include/linux/libata.h
> +++ b/include/linux/libata.h
> @@ -1157,6 +1157,12 @@ extern int ata_scsi_change_queue_depth(struct scsi_device *sdev,
> int queue_depth);
> extern int ata_change_queue_depth(struct ata_port *ap, struct scsi_device *sdev,
> int queue_depth);
> +extern int ata_ncq_prio_supported(struct ata_port *ap, struct scsi_device *sdev,
> + bool *supported);
> +extern int ata_ncq_prio_enabled(struct ata_port *ap, struct scsi_device *sdev,
> + bool *enabled);
> +extern int ata_ncq_prio_enable(struct ata_port *ap, struct scsi_device *sdev,
> + bool enable);
> extern struct ata_device *ata_dev_pair(struct ata_device *adev);
> extern int ata_do_set_mode(struct ata_link *link, struct ata_device **r_failed_dev);
> extern void ata_scsi_port_error_handler(struct Scsi_Host *host, struct ata_port *ap);
> --
> 2.44.0.278.ge034bb2e1d-goog
>